Double microwave resonances have been observed in cobalt ferrite when a magnetic field was applied in crystal directions near the hard axis. One resonance occurs before the magnetization vector is lined up with the external magnetic field and another occurs in the aligned state. The experimental results exhibit characteristic features expected before complete line-up and yield, at 90°C, $\frac{K_1}{M}=2200\mathrm{}\pm 200$ and $g=2.7\mathrm{}\pm 0.3$.

• Received 1 April 1955

DOI:https://doi.org/10.1103/PhysRev.99.463